A dimmable fluorescent lamp is desired by the public for a long time. Unlike an incandescence lamp which can effect dimming with a common silicon controlled rectifier (SCR) dimmer, a fluorescent lamp is a nonlinear load and exhibits a negative resistance characteristic such that it cannot effect dimming with the regular SCR dimmer. In the available domestic and commercial dimmers a TRIAC is usually employed, and a characteristic of which is the requirement of a holding current for maintaining the on state thereof after it has been triggered. The characteristic suits the operation modes of a resistive load such as an incandescence lamp so well but being undesired by a capacitive load such as a fluorescent lamp, for the reason that blinking might occur owing to the discontinuity and instability in course of dimming operation while such dimmers are employed, which in turns has an adverse effect on the illumination effect and the life span of the fluorescent lamp. In this way, the incandescence lamp having high power consumption and short lifespan is the only choice for those who want to use a dimmer to enjoy dimming function and effect.